1. Field of the Invention
The present invention relates to an optical fiber length adjuster to be attached to a device having an optical fiber therein and adjust the length of the optical fiber.
2. Description of the Related Art
There has heretofore been a device having an optical fiber therein such as an endoscope. In the endoscope, a light source is connected to a proximal end side of an elongated insertion portion to be inserted into the body or lumen of an observation target. Light from the light source is guided by the optical fiber from the light source outside the endoscope to the distal end of the insertion portion of the endoscope.
On the other hand, a body insertion portion of a medical flexible endoscope is designed to be sufficiently curvable. In the actual insertion into the body as well, the distal end of the endoscope is inserted into the body while the insertion portion is curved. When an optical fiber is incorporated in this curvable insertion portion of the endoscope, the necessary length of the optical fiber differs between the curved state of the endoscope insertion portion and the straight state (uncurved state) of the endoscope insertion portion. For example, when the endoscope insertion portion is in the straight state, the necessary length of the optical fiber is smallest. In contrast, when the endoscope insertion portion is curved, the length of the optical fiber is greater than in the straight state. Therefore, tensile force is applied to the optical fiber when the length of the optical fiber incorporated in the insertion portion of the endoscope is smaller the necessary length. When the length of the optical fiber incorporated in the insertion portion of the endoscope is greater than the necessary length, the optical fiber is superfluous, and the optical fiber may buckle in the middle part.
Japanese Patent No. 4732783 shows an endoscope having the following configuration. One optical fiber is incorporated in an insertion portion of the endoscope. A fluorescent material is provided at the distal end of the insertion portion. One end of a universal cord is coupled to an operation portion connected to the proximal end of the insertion portion. The other end of the universal cord is coupled to a processor unit. A laser light source is provided inside the processor unit. Light from the laser light source is guided to the distal end of the endoscope insertion portion through one optical fiber. When excitation light is applied to the fluorescent material, white fluorescence in which red, green, and blue fluorescences are mixed is applied.
If a light guide member is changed from a bundle fiber to one optical fiber as in Japanese Patent No. 4732783, the optical fiber may break when the light guide member is bent. In this case, it is highly possible that the amount of illumination light emitted from the distal end of the light guide member may considerably decrease. More specifically, a large number, for example, several thousand thin fibers are bundled in the bundle fiber, so that the influence on the illumination light amount is small even if several ones of a large number of optical fibers constituting the bundle fiber have broken when the bundle fiber is bent. In contrast, in the case where one optical fiber is incorporated in the insertion portion of the endoscope, if the optical fiber breaks when the optical fiber is bent, the illumination light amount reaches zero because no laser light is guided.
Particularly in the case of the endoscope having the flexible insertion portion, it is highly possible that the optical fiber may break because of buckling or pulling as a result of repeated deformation of the endoscope insertion portion into the straight state and the curved state. The optical fiber movably disposed inside the insertion portion may fit into the space between contents such as electric cables and tubes disposed around the optical fiber so that the necessary length is smaller in the curved state than in the straight state.
On the other hand, when the optical fiber is caught between contents such as electric cables and tubes disposed around the optical fiber, the necessary length is greater in the curved state than in the straight state. That is, as a result of repeated deformation of the endoscope insertion portion into the straight state and the curved state, the optical fiber inside is repeatedly compressed and pulled, which increases the possibility that the optical fiber may buckle or break.
The present invention has been made in view of the foregoing circumstances, and is intended to provide an optical fiber length adjuster capable of preventing an optical fiber from breaking when the optical fiber is disposed in a device to vary necessary length.